The overall objectives of this project are to extend our knowledge of the basic enzymology and regulation of the mammalian protein phosphatases, using liver phosphorylase phosphatase as a model enzyme. These objectives include: (1) isolation and characterization of the active and inactive forms of liver and heart phosphorylase phosphatase; (2) the clarification of the relationship between the active and inactive forms of phosphorylase phosphatase; (3) the characterization of a protein inhibitor of the enzyme; (4) the possible hormonal regulation of the enzyme. BIBLIOGRAPHIC REFERENCES: Properties and Regulation of Liver Phosphorylase Phosphatase. E.Y.C. Lee, H. Brandt, Z.L. Capulong and S.D. Killilea In Advances in Enzyme Regulation, Vol. 14, 467-490 (1976). Multiple Forms of Phosphorylase Phosphatase. S.D. Killilea, M.E. Metieh and E.Y.C. Lee Fed. Proc. 35, 1410 (1976).